1. Field of the Invention
The present invention relates to communication systems. More specifically, the present invention relates to receivers with signal processors for determining the location of a transmitter and the time of arrival of a pulse therefrom.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility
2. Description of the Related Art
In many applications, there is a need to determine the time and angle of arrival of a transmitted pulse. For example, in military applications, the conventional technique for determining the ability of a gunner to hit a target with a munition is visual. That is, the target is simply visually examined to determine the number of hits or score.
Unfortunately, the visual scoring method is costly due to the requirement that the target be retrieved and examined to provide a score. Visual scoring from a remote location is often complicated by numerous range and/or battlefield conditions including darkness, haze, smoke, dust, and etc. In addition, there is no real time feedback of a gunners score during the firing operation. Accordingly, the opportunity for real time correction is not provided with conventional scoring techniques
U.S. patent application entitled RADIO FREQUENCY DEVICE FOR MARKING MUNITION IMPACT POINT, U.S. Pat. No. 5,280,751, by J. O. Muirhead and G. E. Held discloses a unique and advantageous automatic system for gunnery scoring The system includes a plurality of miniature radio transmitters which are mounted on one or more of the munitions. The transmitters are energized when the projectile impacts the target. The transmitted signal is detected by one or more receivers. Detection occurs when the received signal exceeds a fixed threshold. By accurately monitoring the time of arrival at a number of different locations, the angle of arrival may be determined at each receiver from which the impact point of the round can be determined by triangulation.
Unfortunately, due to attenuation, the amplitude of the signal transmitted from the impact point varies inversely with the square of the distance from the impact point to the receiver. Thus, each receiver may receive the transmitted signal at a different level. With each receiver having a detector with the same fixed threshold, differences in signal levels translate to differences in the time of detection of the transmitted signal. Differences in the time of detection, contribute to error in the location computations Other sources of error include differences in antenna and receiver gain patterns.
Thus, there is a need in the art for further improvements in gunnery scoring systems utilizing munitions equipped with radio transmitters. More specifically, there is a need in the art for a technique for minimizing computation error due to signal level variations at the receivers of gunnery scoring systems using munitions equipped with radio transmitters.